1. Field of the Invention
The invention pertains to the art of tools and methods for removing a tube from a multi-tube finned heat exchange coil of the type in which the tubes are expanded into the fins throughout the length of the tube.
2. Description of the Prior Art
To best understand the application of the invention, a brief description of the general type of heat exchange coil to which it is believed most applicable is in order. Many heat exchange coils are now constructed with a large number of aluminum tubes extending transversely through holes in aluminum fins. After the assembly of the tubes to the fins, the tubes are then expanded outwardly to seat tightly against the fin material defining the holes in which the tubes are situated. Then aluminum end bends and other fittings such as tripods, crossovers, and various headers are placed on the open ends of the tubes and the heat exchanger is subjected to an operation in which these fittings are soldered to the tube ends. The different types of soldering operations which may be used include several, such as flame soldering and superheated air soldering, in which some of the joints may become sufficiently hot that one or more end bends or other fittings may be effectively destroyed along with the bell end of the tube in which the fitting is located. This problem can arise, as explained in U.S. patent application Ser. No. 580,506 filed May 23, 1975, because different fittings present different heat transfer problems so that while that temperature may be quite proper for one type of joint it may be too hot for another particular joint and damage to the tube ends and fittings may result. The problem may also arise from temperature differences at different locations in a superheated air atmosphere or in a flame soldering process. Further, defects in the tube, such as pin holes, splits, cracks etc., can also cause leaks which would require tube removal.
Irrespective of the cause, a tube which has its end damaged sufficiently that the repair cannot take place easily requires that the particular tube be removed. It has been my experience that frequently the damage is sufficient, and the prior art tube removal processes so ineffective, that the practice has been to scrap the entire coil. Since many of the coils include substantial material in the form of tubes, fins and fittings, as well as labor cost invested therein, scrapping of the coils is very costly to the manufacturer.
Processes for removing defective tubes from a heat exchanger are known as evidenced by the following U.S. Patents for example: U.S. Pat. Nos. 3,835,520; 2,731,714; 2,411,246; and 408,162. These patents are generally directed to arrangements for removing a tube from heat exchangers of the tube and shell type or which have a tube sealed at opposite ends in a tube sheet with intermediate transverse plates simply providing tube support. In removing tubes from this type of structure, the process is basically that of loosening or manipulating only the tube ends to a degree sufficient that the tube is loosened thereat, after which the tube may be withdrawn. Such processes may work well with that type of heat exchange structure, but would be totally ineffective with the type of heat exchanger with which the present invention is concerned, and in which the tube is expanded outwardly throughout its total length to seat tightly in the apertures of each of the fins or plates through which the tube passes. In other words, if only the ends of the tubes in the expanded tube heat exchanger were loosened, it would be of little help in permitting the tube to be withdrawn from the heat exchanger as a whole.
One way which has been suggested for removing an expanded tube from a heat exchanger, and which has not been particularly effective, is to slit the wall of the tube longitudinally at two or more locations around the circumference by a device somewhat like a double blade glass cutter which is pushed through the tube.
Finally, there have been various tools, combined with particular methods, devised for removing tubes and pipes from heat exchangers and like apparatus, examples of such patents being U.S. Pat. Nos. 3,729,806, 3,341,930, 3,176,384, and 1,276,458.
None of the above-noted patents teach a method or tool which will permit the removal of an expanded tube sufficiently effectively in my view that the scrapping problem of damaged coils would be avoided. Accordingly, it is the aim of my invention to provide a method and tool which permits the relatively easy removal of expanded tubes, leaving the hole from which the tube was removed in such condition that the tube can be replaced and the coils can be inexpensively salvaged.